Poly(methylphosphate/phosphonate) products have been prepared by the reaction of phosphorus pentoxide with trimethyl phosphate or dimethyl methylphosphonate. The statistical distribution, nuclear magnetic resonance characteristics, and other non-chemical features of phosphate and phosphonate groups in such products are described by R. A. Schep, J. H. H. Coetzee, and S. Norval, THE POLYMER PRODUCTS FORMED WHEN DIMETHYL METHYLPHOSPHONATE REACTS WITH PHOSPHORUS PENTOXIDE, Joernaal Van Die SuidAfrikaanse Chemises Instituut. Band XXVII, 1974, pages 63 to 69.
U.S. Pat. No. 3,099,676 (to W. M. Lanham, patented July 30, 1963) described polyphosphates produced by the reaction of vicinal epoxides with pyrophosphoric acids. Lanham prepares heavily hydroxylated derivatives of pyrophosphoric acid (two phosphorus atoms). An epoxide residue is inserted into the --P(O)--O--P(O)-- portion of the acid.
U.S. Pat. No. 3,639,545 (to R. D. Wilcox, patented Feb. 1, 1972) describes the reaction of a bisalkylene pyrophosphate with vicinal alkylene oxide to form a cyclic alkylene phosphate alkylene ester of the formula: ##STR3## Wilcox prepares products having terminal alkylene groups and an epoxide residue inserted into the phosphorus anhydride structure. The Wilcox products contain two phosphorus atoms.
U.S. Pat. Nos. 3,767,732 (to W. Klose) and 3,850,859 (to J. Wortmann, et al.) describe halogenated phosphorus containing polyols of the general formula: ##STR4## The Klose and Wortmann patents describe compounds having two to six phosphorus atoms in repeating linkages of --P(O)--OR--O--. Each phosphorus atom has a pendant oxyorgano group containing hydroxyl functionality.
U.S. Pat. No. 3,855,359 (to E. D. Weil, patented Dec. 17, 1974) describes copolycondensed vinylphosphonate flame retardants containing as a portion of the repeating units: ##STR5##
U.S. Pat. No. 3,891,727 (to E. D. Weil, patented June 24, 1975) describes fire retardant phosphorus oligomers formed by condensation of beta-haloalkyl esters of pentavalent phosphorus acid. These oligomers may contain repeating units of the general formula: ##STR6##
British Patent No. 1,468,053 (to Stauffer Chemical Co.) describes the condensation of a beta-haloalkylphosphate and a dialkyl phosphonate to yield a halogen free condensation product illustrated by the formula: ##STR7##
The Weil patents and British Pat. No. 1,468,053 describe phosphorus based flame retardants having a --P--(O)--OR--O-- backbone formed from condensation-type reactions. Vinyl, haloalkoxy, or organophosphorus groups pendant from backbone phosphorus atoms are a required feature of structure. The condensation-type reactions do not incorporate all of the starting reactants into the final product. Organic compounds split out during the course of the reaction necessitate purification or byproduct recovery steps.
The condensation-type reactions are preferably conducted at above ambient temperatures. Since these reactions are endothermic energy must be added to the reaction system.